1. Field of the Invention
This invention relates to insect repellents, and in particular to an insect repellent in which the durability of N,N-diethyltoluamide as a repellent ingredient is increased.
2. Description of the Prior Art
Most mosquitoes among various vectors inhabit warm or torrid zones, but could climatically inhabit a cold district. The mosquitoes attack the exposed skin surface during field work, and often cause infectious diseases and endemic diseases.
In order to repel such insect, many studies on insect repellents have been made and, as a result, a variety of compounds possessing a repellent effect have been found. Among them, N,N-diethyltoluamide is the most suitable for practical use in human beings and finds wide usage at present in view of the durability after application and the strength of effect.
However, N,N-diethyltoluamide has the defect in that the compound is absorbed from the skin into the human body when it is applied to the body surface, and consequently, loses its repellency. N,N-diethyltoluamide becomes more durable when employed in increased amounts, but use of such large amounts gives a sticky feeling to the body and is not practically acceptable. As one attempt to inhibit the absorption from the skin into the body, a method has been reported which comprises forming on the skin a film insoluble in N,N-diethyltoluamide and subsequently coating N,N-diethyltoluamide on the film. In this instance, no satisfactory results are obtainable because the film adheres poorly to the skin.